What is a soy allergy?
A soy allergy is a type of food allergy. Your immune system overreacts to soy you’ve ingested (eaten or drunk). For many people, ingesting soy is harmless. However, if you have a soy allergy, your immune system views the protein in soy as a harmful “invader,” like a bacterium or virus.
A soy allergy can be deadly. If you have severe allergic reaction symptoms, such as trouble breathing or swelling in your throat, call 911 or go to your nearest emergency room (ER) immediately.
Who does a soy allergy affect?
A soy allergy can affect anyone of any age. However, infants and young children are more likely to have a soy allergy. You’re also more likely to have a soy allergy if you have other food allergies.
Many infants outgrow a soy allergy as they get older.
Can you develop a soy allergy?
Yes. A soy allergy can appear at any age. Certain foods or drinks you previously ingested without any problems can trigger an allergic reaction.
How common is a soy allergy?
Infants and young children are the most likely to have a soy allergy. Approximately 0.4% of infants in the U.S. are allergic to soy.
How does a soy allergy affect my body?
A soy allergy causes an allergic reaction in your body. An allergic reaction is your body’s response to an allergen. If you have a soy allergy, your body may have two different types of reactions:
Immunoglobulin E-mediated reaction
If you have a soy allergy, your body responds by creating immunoglobulin E (IgE) after your first exposure to soy. IgE is an antibody that your immune system makes. Your body makes many different types of IgE, which target specific kinds of allergens.
IgE reactions happen quickly after ingesting soy. Reactions may include anaphylaxis, which is a severe allergic reaction that may cause death.
Non-immunoglobulin E-mediated reaction
Non-IgE reactions may involve your immune system, but not your IgE antibodies. Your reaction to soy is slower than an IgE-mediated reaction. It may take up to 48 hours to develop.
Most non-IgE food allergies, including soy, aren’t life-threatening. However, soy is one of the most common triggers for a non-IgE reaction in infants.
Reactions may include soy protein intolerance, or eosinophilic esophagitis (EoE). EoE causes inflammation in your esophagus, which is the tube that connects your mouth to your stomach.
Symptoms and Causes
What are the symptoms of a soy allergy?
Soy allergy symptoms include:
- Stomach cramps.
- Nausea and vomiting.
- Tightness in your throat.
- Anaphylaxis (difficulty breathing, increased heart rate, drop in blood pressure, dizziness and confusion).
Can a soy allergy cause stomach issues?
Yes, a soy allergy can cause stomach issues.
You may have stomach cramps, indigestion, diarrhea, nausea and vomiting if you have soy intolerance, which is different than a soy allergy.
Does soy cause inflammation?
Eating a lot of soy may cause inflammation. However, there’s not enough research to conclusively say that soy causes inflammation.
What causes a soy allergy?
Proteins in soy cause your immune system to overreact.
Is a soy allergy contagious?
No, a soy allergy isn’t contagious. You can’t spread a soy allergy to another person.
Diagnosis and Tests
How is a soy allergy diagnosed?
An allergist is a healthcare provider who specializes in allergies. They can help you diagnose your soy allergy through tests.
Before conducting soy allergy tests, they may ask you questions, including:
- Do you have a family history of food allergies?
- Have you ever been diagnosed with other food allergies?
- What are your symptoms?
- Do you take any over-the-counter (OTC) medications to treat your symptoms?
- When do you notice your symptoms start to appear?
- Do you keep a food journal?
What tests will be done to diagnose a soy allergy?
Your allergist may use different allergy tests to help diagnose your soy allergy based on your symptoms. These tests may include:
During a blood test, your allergist will use a thin needle (21 gauge, slightly smaller than the size of a standard earring) to withdraw a small amount of blood from a vein in your arm. The blood sample goes to a laboratory. The lab adds soy proteins to your blood sample and measures the levels of IgE antibodies in it.
It may take a week or longer to get the results from a blood test sent to a lab.
Skin prick (scratch) test
This test exposes your body to small amounts of soy proteins.
Your allergist will first clean a test area of your skin with iodine or alcohol. The test area is usually on your forearm or upper back.
Your allergist will use a thin needle (lancet) to prick your skin with a small amount of liquid containing soy proteins. The lancet won’t go deep into your skin. You’ll only feel a tiny pinch, and you won’t bleed.
Some allergists may use a different method for skin testing. They place a droplet of liquid soy proteins on your skin. They then use a lancet to scratch your skin lightly. The droplets will enter your skin through the scratch. You’ll only feel slight discomfort, and you won’t bleed.
After skin testing, you’ll wait 15 minutes. The allergist will then measure any discolored spots on your skin from the soy test or the controls for the test with a ruler.
A skin prick test takes less than an hour.
Graded oral challenge
To definitively diagnose a food allergy, your allergist may recommend a food challenge. This may be necessary if your family history of food allergies and testing don’t match.
During an oral challenge, you’ll eat a small amount of soy. Your allergist will then observe you to see if a reaction develops. You may gradually eat more soy to see how your body responds.
A graded oral challenge may take up to four hours.
Management and Treatment
How is a soy allergy treated?
If you have a soy allergy, avoiding soy is the only way to prevent a reaction. By law, manufacturers must include soy on the ingredients label of packaged foods sold in the U.S.
If you have a soy allergy, you must consider other possible exposures, including:
- Nonfood items. Certain nonfood items contain soy, including candles, crayons, cleaning products, pet foods, synthetic fabrics and certain makeup and toiletry items. However, labeling laws don’t apply to nonfood items. If you’re unsure of the ingredients in a nonfood item, go to the manufacturer’s website or call their customer service number to get the complete list of product ingredients.
- Shared equipment. During the manufacturing process, some items share equipment or surfaces with soy. Look for labels that say: “Made on equipment shared with soy.”
What foods and drinks should I avoid if I have a soy allergy?
Many different foods and drinks contain soy. These include:
- Soy in all forms, including soy flour, soy fiber, soy albumin and soy grits.
- Soy non-dairy alternatives, including soy milk, soy ice cream, soy cheese and soy yogurt.
- Soybean (curd and granules).
- Soy protein (concentrate, isolate and hydrolyzed).
- Soy nuts and soy sprouts.
- Soy sauce.
- Tofu and textured vegetable protein (TVP).
It’s also a good idea to be aware of foods that contain natural and artificial flavoring, vegetable broth, vegetable gum and vegetable starch. These foods often contain soy protein.
Items that include hydrolyzed plant protein, hydrolyzed vegetable protein, protein extender and protein filler may include soy protein.
Soy may also be present in foods and drinks such as vodka and nut butters.
Can I eat soy lecithin or soybean oil?
Studies show that most people with a soy allergy can safely eat foods that contain soy lecithin and soybean oil. Soybean oil shouldn’t be cold-pressed, expeller-pressed or extruded.
What medications are used to treat a soy allergy?
If you have a soy allergy, your healthcare provider should prescribe you an epinephrine auto-injector (EpiPen®). Epinephrine quickly reverses the symptoms of anaphylaxis. Your provider will explain when and how to use this device. You should keep your epinephrine injector with you at all times.
People who have a soy intolerance or a non-IgE-mediated soy allergy don’t need a prescription for epinephrine.
What are the side effects of epinephrine injections?
Epinephrine injection side effects may include:
- Dry mouth.
- Increased sweating.
- Fatigue (weakness or tiredness).
These symptoms are typically mild if they occur, and they go away quickly.
How soon after treatment will I feel better?
An epinephrine injection starts to work immediately after you’ve injected yourself.
How can I prevent an allergic reaction to soy?
The best way to prevent an allergic reaction to soy is to strictly avoid soy ingredients in foods, drinks and other non-food products.
Check the ingredient labels on all packaged foods. If you’re unsure if a product contains soy, avoid it until you can confirm with the manufacturer.
Outlook / Prognosis
What can I expect if I have a soy allergy?
Living with a soy allergy can be challenging. Symptoms can range from mild to severe, and there’s no way to predict how your body will react. However, with caution, you can leave a fulfilling life. Your healthcare provider can recommend resources, support groups and dietitians to help you with your day-to-day meals.
Infants and young children are more likely to have soy allergies than adults. Most children outgrow a soy allergy by age 10.
When should I see my healthcare provider?
See your healthcare provider if you regularly have soy allergy symptoms or if you notice that your symptoms develop after eating soy.
When should I go to the ER?
Go to the ER or call 911 if you start showing symptoms of anaphylaxis.
What questions should I ask my healthcare provider?
- How can you tell that I have a soy allergy?
- What medications do you recommend?
- What’s the complete list of side effects of your recommended allergy medication?
- When can I introduce soy to my child?
- Will my child outgrow their soy allergy?
- Are there any support groups for people or parents of children who have soy allergies?
- Can you recommend a dietitian?
Frequently Asked Questions
What is the difference between a soy allergy and soy intolerance?
A soy allergy is when your immune system overreacts to soy protein.
A soy intolerance is when your digestive system has a hard time breaking down (digesting) soy. When you ingest soy, you may have symptoms such as gas, diarrhea and abdominal pain.
A note from Cleveland Clinic
A soy allergy is a type of food allergy that occurs when your immune system mistakenly triggers a defensive response to soy. This response — or allergic reaction — can cause various symptoms, including vomiting, stomach cramps, indigestion, diarrhea and, in severe cases, anaphylaxis.
You may feel frustrated not knowing what’s causing your symptoms, but your healthcare provider can help. They can conduct tests to confirm a soy allergy and prescribe medications. They can also refer you to a dietitian who can help you learn what’s best for you to eat and drink.
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